KMP算法实现

#include 
#include 
#include 

using namespace std;

void prefix_table(int prefix[], char pattern[], int n)
{
	int len = 0;
	int j = 1;
	prefix[0] = 0;
	while (j < n)
	{
		if (pattern[j] == pattern[len])
		{
			++len;
			prefix[j] = len;
			++j;
		} 
		else
		{
			if (len > 0)
				len = prefix[len - 1];
			else
			{
				prefix[j] = len;
				++j;
			}
		}
	}
}

void move_prefix_table(int n, int prefix[])
{
	for (int i = n - 1; i >= 1; --i)
		prefix[i] = prefix[i - 1];
	prefix[0] = -1;
}

void kmp_search(char pattern[], char text[])
{
	int n = strlen(pattern);
	int m = strlen(text);
	int *prefix = (int*)malloc(n * sizeof(int));
	prefix_table(prefix, pattern, n);
	move_prefix_table(n, prefix);
	int i = 0, j = 0;
	while (i < m)
	{
		if (j == n - 1 && text[i] == pattern[j])
		{
			cout << "find it at" << i - j << endl;
			j = prefix[j];
		}
		if (pattern[j] == text[i])
		{
			++i;
			++j;
		}
		else {
			j = prefix[j];
			if (j == -1) {
				++j;
				++i;
			}
		}
	}
	free(prefix);
}

int main()
{
	char pattern[] = "ABCABCAAB";
	char text[]    = "AAAABABCABCAABA";
	kmp_search(pattern, text);
	return 0;
}